This invention relates to compounds that contain both epoxy and styrenic or cinnamyl functionality and that can be used in curable compositions.
Curable compositions are used in the fabrication and assembly of semiconductor packages and microelectronic devices, such as in the bonding of integrated circuit chips to lead frames or other substrates, in the bonding of circuit packages or assemblies to printed wire boards, or in encapsulants or coating materials. There are a number of electron donor/electron acceptor adhesive systems that are used in the industry, but not all these give as full performance as is needed for all uses. The compounds disclosed in this specification add to the spectrum of performance materials for use within the semiconductor fabrication industry.
In one embodiment, this invention relates to compounds that contain both epoxy and styrenic or cinnamyl functionality. In another embodiment, this invention is a curable composition, such as an adhesive, coating, or encapsulant composition, containing such compounds.
In one embodiment, this invention is a compound having at least one epoxy group and one styrenic or cinnamyl group per molecule. In another embodiment, this invention is a curable composition, such as an adhesive, coating, or encapsulant, containing the compound with both epoxy and styrenic or cinnamyl functionality. The composition can be a paste, prepared by blending or milling, or can be a film, prepared by standard film making techniques known to those skilled in the art. The curable composition will include optionally a curing agent, and optionally a filler.
These compounds can be the main component in the curable composition or can be added as an adhesion promoter to one or more other curable resins. When used as an adhesion promoter, the amount used in the curable composition will be an effective amount to promote adhesion and, in general, an effective amount will range from 0.005 to 20.0 percent by weight of the formulation.
Examples of other curable resins for use as the main component in the curable compositions include epoxies, vinyl ethers, thiolenes, compounds derived from cinnamyl and styrenic starting compounds, fumarates, maleates, acrylates, and maleimides.
Suitable curing agents are thermal initiators and photoinitiators present in an effective amount to cure the composition. In general, those amounts will range from 0.5% to 30%, preferably 1% to 20%, by weight of the total organic material (that is, excluding any inorganic fillers) in the composition. Preferred thermal initiators include peroxides, such as butyl peroctoates and dicumyl peroxide, and azo compounds, such as 2,2xe2x80x2-azobis (2-methyl-propanenitrile) and 2,2xe2x80x2-azobis(2-methyl-butanenitrile). A preferred series of photoinitiators is one sold under the trademark Irgacure by Ciba Specialty Chemicals. In some formulations, both thermal initiation and photoinitiation may be desirable: the curing process can be started either by irradiation, followed by heat, or can be started by heat, followed by irradiation.
In general, the curable compositions will cure within a temperature range of 70xc2x0 C. to 250xc2x0 C., and curing will be effected within a range of ten seconds to three hours. The actual cure profile will vary with the components and can be determined without undue experimentation by the practitioner.
The curable compositions may also comprise nonconductive or thermally or electrically conductive fillers. Suitable conductive fillers are carbon black, graphite, gold, silver, copper, platinum, palladium, nickel, aluminum, silicon carbide, boron nitride, diamond, and alumina. Suitable nonconductive fillers are particles of vermiculite, mica, wollastonite, calcium carbonate, titania, sand, glass, fused silica, fumed silica, barium sulfate, and halogenated ethylene polymers, such as tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride, vinylidene chloride, and vinyl chloride. If present, fillers generally will be in amounts of 20% to 90% by weight of the formulation.
In another embodiment, this invention is a curable composition comprising the compound having at least one epoxy group and at least one styrenic or cinnamyl group per molecule and an epoxy resin. In a preferred embodiment, the epoxy resin has the structure 
The following Examples disclose representative compounds containing at least one epoxy group and one styrenic or cinnamyl group per molecule and the synthetic procedures for making those compounds. Also disclosed is the performance of samples in curable compositions.